Segment Results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 item	Mar. 31, 2014
Segment Results
Number of reportable segments	3
Earnings Summary:
Net interest income	$ 216,580	$ 199,798
Provision for losses on covered loans	497	4,655
Noninterest income	111,075	101,248
Depreciation and amortization	16,359	9,315
Noninterest expense	218,083	201,537
Income before income taxes	92,716	85,539
Provision for income taxes	30,597	31,010
Net income	62,119	54,529
Less: Net income attributable to noncontrolling interest	553	699
Net income attributable to City National Corporation	61,566	53,830
Selected Average Balances:
Loans and leases, excluding covered loans	20,404,720	17,338,419
Covered loans	492,438	696,163
Total assets	32,259,619	29,413,998
Deposits	27,808,383	25,371,598
Goodwill	635,868	642,622
Customer-relationship intangibles, net	34,184	40,055
Other segment
Earnings Summary:
Net interest income	7,947	9,765
Noninterest income	(15,510)	(9,460)
Depreciation and amortization	11,783	4,747
Noninterest expense	(26,402)	(18,372)
Income before income taxes	7,056	13,930
Provision for income taxes	2,342	5,091
Net income	4,714	8,839
Net income attributable to City National Corporation	4,714	8,839
Selected Average Balances:
Loans and leases, excluding covered loans	56,617	55,009
Total assets	10,554,163	10,516,708
Deposits	170,668	232,082
Commercial and Private Banking
Earnings Summary:
Net interest income	207,826	189,708
Provision for losses on covered loans	497	4,655
Noninterest income	51,496	47,142
Depreciation and amortization	2,715	2,821
Noninterest expense	189,882	167,695
Income before income taxes	66,228	61,679
Provision for income taxes	21,987	22,544
Net income	44,241	39,135
Net income attributable to City National Corporation	44,241	39,135
Selected Average Balances:
Loans and leases, excluding covered loans	20,348,103	17,283,410
Covered loans	492,438	696,163
Total assets	20,960,198	18,239,567
Deposits	27,549,867	25,051,747
Goodwill	393,177	393,177
Customer-relationship intangibles, net	1,650	3,134
Wealth Management
Earnings Summary:
Net interest income	807	325
Noninterest income	75,089	63,566
Depreciation and amortization	1,861	1,747
Noninterest expense	54,603	52,214
Income before income taxes	19,432	9,930
Provision for income taxes	6,268	3,375
Net income	13,164	6,555
Less: Net income attributable to noncontrolling interest	553	699
Net income attributable to City National Corporation	12,611	5,856
Selected Average Balances:
Total assets	745,258	657,723
Deposits	87,848	87,769
Goodwill	242,691	249,445
Customer-relationship intangibles, net	$ 32,534	$ 36,921